For example, inkjet heads, in which an actuator formed of PZT is adhered onto a substrate formed of alumina by using an epoxy-based adhesive, are known. According to the inkjet heads of this type, the actuator includes a plurality of grooves which are filled with ink. The grooves are arranged at intervals in a longitudinal direction of the actuator, and continuously opened to the surface and side surfaces of the actuator. The side surfaces of the actuator are inclined from the surface of the actuator toward the substrate, to project from the actuator sideward. The adhesive is filled into a space between the substrate and the actuator, and forms an adhesive layer between the substrate and the actuator. The adhesive layer includes an end part which is exposed from a space between the side surfaces of the actuator and the substrate.
Internal surfaces of the grooves of the actuator are provided with respective electrodes. The electrodes are formed by continuously covering the internal surfaces of the grooves of the actuator, the side surfaces of the actuator, and the substrate with a plating layer, and thereafter irradiating the plating layer with laser light from above.
A part of the plating layer, which is irradiated with laser light, defines a plurality of insulating patterns. The insulating patterns divide the plating layer into a plurality of electrodes, and cross the end part of the adhesive layer through a space between adjacent grooves and reach the substrate.
According to inkjet heads of prior art, the air is sometimes taken into the adhesive when the actuator is adhered onto the substrate. The taken air remains in the adhesive layer as an air bubble. When the air bubble is located in the end part of the adhesive layer, the end part of the adhesive layer includes a depression. In addition, the depression is covered with the plating layer together with the side surfaces of the actuator and the substrate, when the electrodes are formed.
The depression is more depressed than the side surfaces of the actuator. Therefore, even when the worker tries to remove the plating layer which covers the depression by laser light, the side surfaces of the actuator blocks the laser light which goes toward the depression. In other words, the laser light does not reach the depression, and the plating layer in the depression is left without being removed by the laser light. As a result, the insulating patterns are interrupted in a position of the depression of the adhesive layer. Therefore, the depression generated in the adhesive layer causes a short between electrodes which are adjacent to each other with the insulating pattern interposed therebetween.